1. Field of the Invention
The present invention relates to a toner consumption-calculating apparatus, which calculates consumption of toner that adheres on a latent image-bearing member of an image forming apparatus such as a copier, a printer, a facsimile etc., the image forming apparatus that includes the toner consumption-calculating apparatus, and a toner consumption calculating method.
2. Description of the Related Art
In an image forming apparatus, which forms an image using toner, a mechanism that can report to a user, toner consumption or a remaining toner amount is desirable for maintenance such as toner replenishment. Due to this, the toner consumption needs to be calculated every time the image formation is performed.
In a commonly used method for calculating the toner consumption, a number of individual dots that form an image from image data are counted, and the toner consumption is calculated by assuming that the number of dots is proportional to the toner consumption. However, because a relation between a continuity of the dots that form a toner image and the toner consumption is nonlinear, the toner consumption cannot be accurately calculated by simply multiplying the number of the dots by the toner consumption per dot. Because an interference degree of an exposure beam changes according to an alignment (density) of the dots, an area of a printed portion based on the image data differs from an area of a latent image portion on a photosensitive drum. Moreover, due to an edge effect resulting from a sharp change in a surface potential of the latent image portion and a non-latent image portion in a boundary vicinity of the latent image portion and the non-latent image portion on the photosensitive drum, a large amount of toner adheres on a boundary vicinity portion of the latent image portion with the non-latent image portion compared to a central portion of the latent image portion. Due to this, the relation between the continuity of the dots and the toner consumption becomes nonlinear.
In an image forming apparatus disclosed in Japanese Patent Laid-open Application No. 2006-171023, based on the image data, a toner consumption-calculating unit is used to calculate the toner consumption along with development of the image corresponding to the image data and the calculated toner consumption is multiplied by a predetermined correction factor that is less than 1 to carry out a correction of the toner consumption. For example, if the maximum value of an error between the calculated toner consumption and the actual toner consumption is plus or minus 20 percent, correction is carried out such that the corrected toner consumption is less than or equal to 80 percent of the calculated toner consumption.
In an image forming apparatus that is disclosed in Japanese Patent Laid-open Application No. 2005-208461, a correction process is carried out based on a quantitative analysis of the relation between the continuity of the dots and the toner consumption. To be specific, a value (toner adhesion amount) is obtained by dividing a total amount of the toner that adheres on a single dot portion by a length of the dot portion and a correlation is calculated between the toner adhesion amount and a size of the dot portion in a main scanning direction. Data related to a dot size is integrated and a process is carried out to correct the nonlinearity between the dot size and the toner consumption.
However, in the correction that is carried out by the image forming apparatus disclosed in Japanese Patent Laid-open Application No. 2006-171023, because the calculated toner consumption is greater than the actual toner consumption, the toner is excessively replenished at the time of toner replenishment. To prevent excessive toner replenishment, the calculated toner consumption is reduced to less than the actual toner consumption. Thus, in the correction mentioned earlier, because the calculated toner consumption is not approximately equal to the actual toner consumption, the toner consumption cannot be precisely calculated by using a calculation.
Although the image forming apparatus disclosed in Japanese Patent Laid-open Application No. 2005-208461 carries out a correcting process of the toner adhesion amount using the alignment (density) of the dots in the main scanning direction, the image forming apparatus does not carry out the correcting process of the toner adhesion amount using the alignment (density) of the dots in a vertical scanning direction. Due to this, a difference between the calculated toner consumption and the actual toner consumption using the alignment of the dots in the vertical scanning direction cannot be detected. Thus, a precision in the calculation of the toner consumption needs to be further enhanced.